﻿
#include <iostream>
#include <cstring>
template <typename T>
class vector
{
public:
    T* first;
    T* last;
    T* end;
    //无参构造
    vector() :first(NULL), last(NULL), end(NULL)
    {
    }
    //有参构造
    vector(int n, const T& val)
    {
        first = new T[n];
        last = first + n;
        end = first + n;
        for (int i = 0; i < n; i++)
        {
            *(first + i) = val;
        }
    }
    vector(const T* s, const T* end2)
    {
        first = new T[end2 - s];
        end = first + (end2 - s);
        last = first;
        for (int i = 0; i < (end2 - s); i++)
        {
            *last = *(s + i);
            last++;
        }
    }
    int size()//输出大小
    {
        if (NULL == first)
            return 0;
        else
            return last - first;
    }
    int capacity() //输出容器最大容量
    {
        if (NULL == first)
            return 0;
        else
            return end - first;
    }
    void push_back(const T& val)//尾插
    {
        if (first == NULL)//判断是否是空
        {
            first = new T;
            last = first;
            end = first + 1;
        }
        if (last == end)
        {
            int s_ize = end - first;
            T* temp = new T[2 * s_ize];
            memset(temp, 0, 2 * sizeof(T) * s_ize);
            memcpy(temp, first, sizeof(T) * s_ize);
            delete[]first;
            first = temp;
            last = first + s_ize;
            end = first + 2 * (s_ize);
        }
        *last = val;
        last = last + 1;
    }
    void pop_back()//尾删
    {
        last--;
    }
    T& at(int num)//定位
    {
        return *(first + num);
    }
};
int main()
{
    vector<int> v1;        //定义一个容器


    std::cout << "v1.size = " << v1.size() << std::endl;      //输出容器的大小
    std::cout << "v1.capacity = " << v1.capacity() << std::endl;  //输出容器的最大容量


    std::cout << "-------------------------------------------------------\n";


    for (int i = 1; i <= 20; i++) //输入二十个数
    {
        v1.push_back(i);
       std:: cout << "v1.size = " << v1.size() << "    v1.capacity = " << v1.capacity() << std::endl;
        //左边是当前容器的大小  右边是容器的最大容量
    }


    //输出当前vector中的内容
    for (auto i = 0; i < v1.size(); i++)
    {
        //cout<<v1[i]<<" ";
        std::cout << v1.at(i) << " ";
    }
    std::cout << std::endl;
    return 0;
}
